Учебное пособие Казань-2016 Сайфуллина М. Н., Хабирова Н. М. English for Physicists

99 
II.
 
Put the words into the right order. Check your answers with the text. 
1.
rays/ gamma/ comes from/ as/ Some/ cosmic/ radiation/ space. 
2.
with/ a nucleus/ beta/ an excited/ energy/ After/ or/ excess/ alpha/ 
undergoes/ left in/ it is/ decay/ state/ often. 
3.
was/ in / A. H. Becquerel/ Radioactivity/ by/ 1896/ discovered. 
4.
emit/ a/ nucleus/ will/ or/ waves/ When/ it/ particles/ some/ decays. 
5.
gives out/ decay/ a/ process/ heat/ Radioactivity/ random/ which/ is. 
III.
 
Guess the words: 
1)
seod 
2)
barobs 
3)
tafal 
4)
cyade 
5)
lentmee 
IV.
 
Skim the passage as fast as possible and find answers to the following 
questions. 
1)
What is the main problem in maintaining a steady chain reaction? 
2)
What are "control rods" used for? 
3)
What is the design of a "swimming pool" reactor? 
4)
What purposes are nuclear power reactors used for? 
Nuclear reactors 
A sample of fissionable material smaller than the "critical size" is 
unable to carry on a nuclear chain reaction. If the size of the sample is 
exactly critical, the number of neutrons produced in each generation is the 
same as that produced in the previous one, resulting in steady nuclear 
energy liberation. The original Fermi-pile and its later modifications 
maintain nuclear reactions at the critical size level. 
It must be mentioned in 
this connection that the conditions of "criticality" are extremely unstable: a 
small deviation (отклонение) in one direction will result in the rapid 
extinction (уменьшение количества нейтронов) of fission neutrons and 
the cut-off of the nuclear chain reaction, whereas a deviation in another 
direction will lead to a rapid multiplication of the fission neutrons and the 
melting (плавление) of the entire structure. 

100 
Thus, the important problem in maintaining a steady chain reaction is 
that of regulating the rate of neutron production and of keeping the chain 
reaction from "dying out" or "running away". 
This is achieved by using 
"control rods" made from neutron-absorbing materials (such as boron) 
which arc automatically pushed in or pulled out from narrow channels 
drilled through the reacting fissionable material as soon as the rate of 
neutron production drops below or exceeds the desired level. 
We have already mentioned that Fermi-piles were unsuitable for 
purposes of nuclear power production because of the high dilution of 
uranium by carbon; they should be considered rather as "alchemical plants" 
in which plutonium is produced. For the purpose of nuclear power 
production, we use the controlled nuclear chain reactions in pure fissionable 
materials, such as U235 or Pu234, which can be run at quite high 
temperatures. 
In the so-called "swimming pool" reactor (реактор бассейнового 
типа) in which several cylindrical containers filled with pure fissionable 
material arc placed at the bottom of a large water tank, the water 
circulating through the tank carries away the heat produced in the fission 
process and also protects the observer from the deadly nuclear radiation. 
The color of the water turns blue as a result of the so-called Cherenkoffs 
radiation produced in water by high-energy electron. 
(Adopted from 
www.studfiles.ru 
) 
 
 
 

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